Method and apparatus for transmitting data on resource unit including pilot tone in WLAN

ABSTRACT

An access point device and method for: generating and transmitting a physical layer protocol data unit (PPDU) including a plurality of resource units on a bandwidth, where the plurality of resource units includes a first tone unit and a second tone unit. The first tone unit includes a total of 26 tones, where 2 pilot tones for the first tone unit are included in the total of 26 tones. The second tone unit includes a plurality of tones being greater than the total of 26 tones. The 4 pilot tones for the second tone unit are included in the plurality of tones. The locations of a plurality of pilot tones for the plurality of resource units are fixed when two first tone units are included in the plurality of resource units in place of the second tone unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the National Stage filing under 35 U.S.C. 371 ofInternational Application No. PCT/KR2015/010570, filed on Oct. 6, 2015,which claims the benefit of U.S. Provisional Application No. 62/060,018,filed on Oct. 6, 2014 and 62/063,931, filed on Oct. 14, 2014, thecontents of which are all hereby incorporated by reference herein intheir entirety.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to wireless communication, and moreparticularly, to a method and apparatus for transmitting data on aresource unit including a pilot tone in a wireless local area network(WLAN).

Related Art

Discussion for a next-generation wireless local area network (WLAN) isin progress. In the next-generation WLAN, an object is to 1) improve aninstitute of electronic and electronics engineers (IEEE) 802.11 physical(PHY) layer and a medium access control (MAC) layer in bands of 2.4 GHzand 5 GHz, 2) increase spectrum efficiency and area throughput, 3)improve performance in actual indoor and outdoor environments such as anenvironment in which an interference source exists, a denseheterogeneous network environment, and an environment in which a highuser load exists, and the like.

An environment which is primarily considered in the next-generation WLANis a dense environment in which access points (APs) and stations (STAs)are a lot and under the dense environment, improvement of the spectrumefficiency and the area throughput is discussed. Further, in thenext-generation WLAN, in addition to the indoor environment, in theoutdoor environment which is not considerably considered in the existingWLAN, substantial performance improvement is concerned.

In detail, scenarios such as wireless office, smart home, stadium,Hotspot, and building/apartment are largely concerned in thenext-generation WLAN and discussion about improvement of systemperformance in a dense environment in which the APs and the STAs are alot is performed based on the corresponding scenarios.

In the next-generation WLAN, improvement of system performance in anoverlapping basic service set (OBSS) environment and improvement ofoutdoor environment performance, and cellular offloading are anticipatedto be actively discussed rather than improvement of single linkperformance in one basic service set (BSS). Directionality of thenext-generation means that the next-generation WLAN gradually has atechnical scope similar to mobile communication. When a situation isconsidered, in which the mobile communication and the WLAN technologyhave been discussed in a small cell and a direct-to-direct (D2D)communication area in recent years, technical and business convergenceof the next-generation WLAN and the mobile communication is predicted tobe further active.

SUMMARY OF THE INVENTION

The present invention provides a method of transmitting data on aresource unit including a pilot tone in a wireless local area network(WLAN).

The present invention also provides a wireless device for performing amethod of transmitting data on a resource unit including a pilot tone ina WLAN.

According to one aspect of the present invention, there is provided amethod of transmitting data on a resource unit including a pilot tone ina WLAN. The method may include: scheduling, by an access point (AP),each of a plurality of wireless resources for communicating with aplurality of stations (STAs) on a bandwidth; and transmitting, by theAP, a plurality of pieces of downlink data to each of the plurality ofSTAs through each of the plurality of wireless resources. At least onewireless resource among the plurality of wireless resources may be avirtual allocation resource unit. The virtual allocation resource unitmay be a combination of at least one first resource unit and at leastone second resource unit including a plurality of data tones that can beinterleaved by one interleaver. A set of positions of a plurality offirst pilot tones included in the virtual allocation resource unit maybe included in a set of positions of a plurality of second pilot tonesincluded in at least one first resource unit and at least one secondresource unit.

According to another aspect of the present invention, there is providedan AP for transmitting data on a resource unit including a pilot tone ina WLAN. The AP may include: a radio frequency (RF) unit for transmittingand receiving a radio signal; and a processor operatively coupled to theRF unit. The processor may be configured for: scheduling each of aplurality of wireless resources for communicating with a plurality ofSTAs on a bandwidth; and transmitting a plurality of pieces of downlinkdata to each of the plurality of STAs through each of the plurality ofwireless resources. At least one wireless resource among the pluralityof wireless resources may be a virtual allocation resource unit. Thevirtual allocation resource unit may be a combination of a plurality ofresource units including a plurality of data tones that can beinterleaved by one interleaver. A set of positions of a plurality offirst pilot tones included in the virtual allocation resource unit maybe included in a set of positions of a plurality of second pilot tonesincluded in the plurality of resource units.

When a wireless resource is allocated for each of a plurality ofstations (STAs) on the basis of orthogonal frequency division multipleaccess (OFDMA), a resource may be allocated to each of the plurality ofSTAs by using a wireless resource unit having a different size bydefinition. Accordingly, scheduling flexibility may be increased, and athroughput of a wireless local area network (WLAN) may be increased.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

FIG. 2 is a conceptual view illustrating a method of allocating wirelessresources according to an embodiment of the present invention.

FIG. 3 is a conceptual view illustrating a method of allocating a pilottone for a virtual allocation resource unit according to an embodimentof the present invention.

FIG. 4 is a conceptual view illustrating a method of allocating a pilottone for a virtual allocation resource unit according to an embodimentof the present invention.

FIG. 5 is a conceptual view illustrating a method of allocating a pilottone in a physical protocol data unit (PPDU) according to an embodimentof the present invention.

FIG. 6 is a conceptual view illustrating a method of allocating a pilottone according to an embodiment of the present invention.

FIG. 7 is a conceptual view illustrating a method of allocating a pilottone according to an embodiment of the present invention.

FIG. 8 is a flowchart illustrating a scheduling method of a wirelessresource according to an embodiment of the present invention.

FIG. 9 is a conceptual view illustrating a downlink (DL) multi-user (MU)PPDU format according to an embodiment of the present invention.

FIG. 10 is a conceptual view illustrating transmission of an uplink (UL)MU PPDU according to an embodiment of the present invention.

FIG. 11 is a block diagram illustrating a wireless device according toan embodiment of the present invention.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 is a conceptual view illustrating the structure of a wirelesslocal area network (WLAN).

An upper part of FIG. 1 illustrates the structure of an infrastructurebasic service set (BSS) of institute of electrical and electronicengineers (IEEE) 802.11.

Referring the upper part of FIG. 1, the wireless LAN system may includeone or more infrastructure BSSs 100 and 105 (hereinafter, referred to asBSS). The BSSs 100 and 105 as a set of an AP and an STA such as anaccess point (AP) 125 and a station (STA1) 100-1 which are successfullysynchronized to communicate with each other are not concepts indicatinga specific region. The BSS 105 may include one or more STAs 105-1 and105-2 which may be joined to one AP 130.

The BSS may include at least one STA, APs providing a distributionservice, and a distribution system (DS) 110 connecting multiple APs.

The distribution system 110 may implement an extended service set (ESS)140 extended by connecting the multiple BSSs 100 and 105. The ESS 140may be used as a term indicating one network configured by connectingone or more APs 125 or 230 through the distribution system 110. The APincluded in one ESS 140 may have the same service set identification(SSID).

A portal 120 may serve as a bridge which connects the wireless LANnetwork (IEEE 802.11) and another network (e.g., 802.X).

In the BSS illustrated in the upper part of FIG. 1, a network betweenthe APs 125 and 130 and a network between the APs 125 and 130 and theSTAs 100-1, 105-1, and 105-2 may be implemented. However, the network isconfigured even between the STAs without the APs 125 and 130 to performcommunication. A network in which the communication is performed byconfiguring the network even between the STAs without the APs 125 and130 is defined as an Ad-Hoc network or an independent basic service set(IBSS).

A lower part of FIG. 1 illustrates a conceptual view illustrating theIBSS.

Referring to the lower part of FIG. 1, the IBSS is a BSS that operatesin an Ad-Hoc mode. Since the IBSS does not include the access point(AP), a centralized management entity that performs a managementfunction at the center does not exist. That is, in the IBSS, STAs 150-1,150-2, 150-3, 155-4, and 155-5 are managed by a distributed manner. Inthe IBSS, all STAs 150-1, 150-2, 150-3, 155-4, and 155-5 may beconstituted by movable STAs and are not permitted to access the DS toconstitute a self-contained network.

The STA as a predetermined functional medium that includes a mediumaccess control (MAC) that follows a regulation of an Institute ofElectrical and Electronics Engineers (IEEE) 802.11 standard and aphysical layer interface for a radio medium may be used as a meaningincluding all of the APs and the non-AP stations (STAs).

The STA may be called various a name such as a mobile terminal, awireless device, a wireless transmit/receive unit (WTRU), user equipment(UE), a mobile station (MS), a mobile subscriber unit, or just a user.

Hereinafter, in the embodiment of the present invention, data(alternatively, or a frame) which the AP transmits to the STA may beexpressed as a terms called downlink data (alternatively, a downlinkframe) and data (alternatively, a frame) which the STA transmits to theAP may be expressed as a term called uplink data (alternatively, anuplink frame). Further, transmission from the AP to the STA may beexpressed as downlink transmission and transmission from the STA to theAP may be expressed as a term called uplink transmission.

In addition, a PHY protocol data unit (PPDU), a frame, and datatransmitted through the downlink transmission may be expressed as termssuch as a downlink PPDU, a downlink frame, and downlink data,respectively. The PPDU may be a data unit including a PPDU header and aphysical layer service data unit (PSDU) (alternatively, a MAC protocoldata unit (MPDU)). The PPDU header may include a PHY header and a PHYpreamble and the PSDU (alternatively, MPDU) may include the frame orindicate the frame (alternatively, an information unit of the MAC layer)or be a data unit indicating the frame. The PHY header may be expressedas a physical layer convergence protocol (PLCP) header as another termand the PHY preamble may be expressed as a PLCP preamble as anotherterm.

Further, a PPDU, a frame, and data transmitted through the uplinktransmission may be expressed as terms such as an uplink PPDU, an uplinkframe, and uplink data, respectively.

In the conventional wireless LAN system, the whole bandwidth may be usedfor downlink transmission to one STA and uplink transmission to one STA.Further, in the wireless LAN system to which the embodiment of thepresent description is applied, the AP may perform downlink (DL)multi-user (MU) transmission based on multiple input multiple output (MUMIMO) and the transmission may be expressed as a term called DL MU MIMOtransmission.

In the wireless LAN system according to the embodiment, an orthogonalfrequency division multiple access (OFDMA) based transmission method issupported for the uplink transmission and/or downlink transmission. Indetail, in the wireless LAN system according to the embodiment, the APmay perform the DL MU transmission based on the OFDMA and thetransmission may be expressed as a term called DL MU OFDMA transmission.When the DL MU OFDMA transmission is performed, the AP may transmit thedownlink data (alternatively, the downlink frame and the downlink PPDU)to the plurality of respective STAs through the plurality of respectivefrequency resources on an overlapped time resource. The plurality offrequency resources may be a plurality of subbands (alternatively, subchannels) or a plurality of resource units (RUs) (alternatively, basictone units or small tone units). The DL MU OFDMA transmission may beused together with the DL MU MIMO transmission. For example, the DL MUMIMO transmission based on a plurality of space-time streams(alternatively, spatial streams) may be performed on a specific subband(alternatively, sub channel) allocated for the DL MU OFDMA transmission.

Further, in the wireless LAN system according to the embodiment, uplinkmulti-user (UL MU) transmission in which the plurality of STAs transmitsdata to the AP on the same time resource may be supported. Uplinktransmission on the overlapped time resource by the plurality ofrespective STAs may be performed on a frequency domain or a spatialdomain.

When the uplink transmission by the plurality of respective STAs isperformed on the frequency domain, different frequency resources may beallocated to the plurality of respective STAs as uplink transmissionresources based on the OFDMA. The different frequency resources may bedifferent subbands (alternatively, sub channels) or different resourcesunits (RUs). The plurality of respective STAs may transmit uplink datato the AP through different frequency resources. The transmission methodthrough the different frequency resources may be expressed as a termcalled a UL MU OFDMA transmission method.

When the uplink transmission by the plurality of respective STAs isperformed on the spatial domain, different time-space streams(alternatively, spatial streams) may be allocated to the plurality ofrespective STAs and the plurality of respective STAs may transmit theuplink data to the AP through the different time-space streams. Thetransmission method through the different spatial streams may beexpressed as a term called a UL MU MIMO transmission method.

The UL MU OFDMA transmission and the UL MU MIMO transmission may be usedtogether with each other. For example, the UL MU MIMO transmission basedon the plurality of space-time streams (alternatively, spatial streams)may be performed on a specific subband (alternatively, sub channel)allocated for the UL MU OFDMA transmission.

In the legacy wireless LAN system which does not support the MU OFDMAtransmission, a multi-channel allocation method is used for allocating awider bandwidth (e.g., a 20 MHz excess bandwidth) to one terminal. Whena channel unit is 20 MHz, multiple channels may include a plurality of20 MHz-channels. In the multi-channel allocation method, a primarychannel rule is used to allocate the wider bandwidth to the terminal.When the primary channel rule is used, there is a limit for allocatingthe wider bandwidth to the terminal. In detail, according to the primarychannel rule, when a secondary channel adjacent to a primary channel isused in an overlapped BSS (OBSS) and is thus busy, the STA may useremaining channels other than the primary channel. Therefore, since theSTA may transmit the frame only to the primary channel, the STA receivesa limit for transmission of the frame through the multiple channels.That is, in the legacy wireless LAN system, the primary channel ruleused for allocating the multiple channels may be a large limit inobtaining a high throughput by operating the wider bandwidth in acurrent wireless LAN environment in which the OBSS is not small.

In order to solve the problem, in the embodiment, a wireless LAN systemis disclosed, which supports the OFDMA technology. That is, the OFDMAtechnique may be applied to at least one of downlink and uplink.Further, the MU-MIMO technique may be additionally applied to at leastone of downlink and uplink. When the OFDMA technique is used, themultiple channels may be simultaneously used by not one terminal butmultiple terminals without the limit by the primary channel rule.Therefore, the wider bandwidth may be operated to improve efficiency ofoperating a wireless resource.

An example of a time-frequency structure, which is assumed in theWireless LAN system according to this exemplary embodiment may be asdescribed below.

A fast fourier transform (FFT) size/inverse fast fourier transform(IFFT) size may be defined as N-times (wherein N is an integer, e.g.,N=4) of the FFT/IFFT sizes that were used in the legacy WirelessLANsystem. More specifically, as compared to the first part of the HE PPDU,the 4-times size of the FFT/IFFT may be applied to the second part ofthe HE PPDU. For example, 256FFT/IFFT may be applied for a 20 MHzbandwidth, 512FFT/IFFT may be applied for a 40 MHz bandwidth,1024FFT/IFFT may be applied for an 80 MHz bandwidth, and 2048FFT/IFFTmay be applied to a continuous 160 MHz bandwidth or a non-continuous 160MHz bandwidth.

Subcarrier space/spacing may correspond to a 1/N-times size (wherein Nis an integer, e.g., when N=4, 78.125 kHz) of the subcarrier spacingthat was used in the legacy WirelessLAN system.

An IDFT/DFT length (or valid symbol length) that is based on inversediscrete fourier transform (IDFT)/discrete fourier transform (DFT) (orFFT/IFFT) may correspond to N-times of the IDFT/DFT length in the legacyWirelessLAN system. For example, in the legacy WirelessLAN system, incase the IDFT/DFT length is equal to 3.2 μs and N=4, in the WirelessLANsystem according to this exemplary embodiment, the IDFT/DFT length maybe equal to 3.2 μs*4(=12.8 μs).

The length of an OFDM symbol may correspond to the IDFT/DFT lengthhaving a length of a guard interval (GI) added thereto. The length ofthe GI may have diverse values, such as 0.4 μs, 0.8 μs, 1.6 μs, 2.4 μs,and 3.2 μs.

When an OFDMA-based resource allocation method according to anembodiment of the present invention is used, the resource allocationunit defined by different sizes may be used. Specifically, a basic toneunit (BTU) and a small tone unit (STU) may be defined for the resourceallocation based on the OFDMA.

The AP may determine DL transmission resource and/or UL transmissionresource for at least one STA based on such various resource units. TheAP may transmit at least one PPDU to at least one STA through thescheduled DL transmission resource. Further, the AP may receive at leastone PPDU transmitted by at least one STA through the DL transmissionresource.

In comparison with the STU, the BTU may be a relatively larger sizeresource unit. For example, the BTU may be defined as the size of 56tones, 114 tones or the like. The BTU may be defined as the same sizeirrespective of the size of the available bandwidth (e.g., 20 MHz, 40MHz, 80 MHz, 160 MHz, etc.) or defined as a size which is changeddepending on the size of the available bandwidth. For example, the sizeof the BTU may be defined as a relatively large value as the size of theavailable bandwidth increases. The tone may be understood as the same asthe subcarrier.

In comparison with the BTU, the STU may be a relatively small sizeresource unit. For example, the STU may be defined as the size of 26tones.

Resource units such as BTU and STU may be allocated on the entirebandwidth (or available bandwidth) in consideration of the left guardtone and the right guard tone which are located at both ends of theentire bandwidth and are used to reduce interference, and the directcurrent (DC) tone located in the center of the entire bandwidth.Further, the resource units such as BTU and STU may be allocated inconsideration of a leftover tone which may be used for user allocationseparation (or resource allocation for each STA), a common pilot, anautomatic gain control (AGC), a phase tracking, etc.

In the entire bandwidth, the allocation method (allocated number,allocation location, etc) of the resource units such as BTU and STU onthe entire bandwidth may be set in consideration of the resourceutilization efficiency and the scalability (or extensibility) accordingto the entire bandwidth. The allocation method of resource units such asBTU and STU may defined in advance or signaled based on various methods(e.g., a signaling based on a signal field included in the PPDU headerof the PPDU).

Hereinafter, a specific resource allocation method based on BTU and STUwill be described.

FIG. 2 is a conceptual view illustrating a method of allocating wirelessresources according to an embodiment of the present invention.

FIG. 2 discloses resource allocation for all available bandwidths basedon BTU and STU.

Table 1 below discloses the basic resource allocation of BTU and STU onbandwidths of 20 MHz, 40 MHz, and 80 MHz.

TABLE 1 20 MHz 40 MHz 80 MHz Basic tone unit (BTU)  56 tones  56 tones 56 tones Small tone unit (STU) 26 tones Total # of BTUs 2  4  8 Total #of STUs 5 10 21 Total available tones 242 tones 484 tones 994 tones(except guard/DC tones) Possible # of BTUs 1, 2 1, 2 1, 2, 4 allocatedto a STA Possible # of STUs 1, 2, 4, 5 1, 2, 4, 10 1, 2, 4, 21 allocatedto a STA Maximum STA # of 7 14 29 allocations

Referring to FIG. 2 and Table 1, BTU may be defined as 56 tones, and STUmay be defined as 26 tones. One STU may be implemented as two dividedSTUs corresponding to 13 tons based on the DC tone.

2 BTUs and 5 STUs may be allocated for 20 MHz bandwidth including 242available tones. Further, 4 BTUs and 10 STUs may be allocated for 40 MHzbandwidth including 484 available tones, and 8 BTUs and 21 STUs may beallocated for 80 MHz bandwidth including 994 available tones.

1 or 2 BTUs may be allocated with one STA for 20 MHz bandwidth. Further,1 or 2 BTUs may be allocated with 1 STA for 40 MHz bandwidth, and 1, 2or 4 BTUs may be allocated with 1 STA for 80 MHz bandwidth.

1, 2, 4 or 5 STUs may be allocated with 1 STA for 20 MHz bandwidth. Thenumber 5, which is the maximum number of STUs allocatable with 1 STA on20 MHz bandwidth, may be defined as another value in consideration ofthe signaling for the number of STUs allocated to one STA. Further, 1,2, 4 or 10 STUs may be allocated with 1 STA for 40 MHz bandwidth. Thenumber 10, which is the maximum number of STUs allocatable with 1 STA on40 MHz bandwidth, may be defined as another number in consideration ofthe signaling for the number of STUs allocated with 1 STA. Further, 1,2, 4 or 21 STUs may be allocated with 1 STA for 80 MHz bandwidth. Thenumber 21, which is the maximum number of STUs allocatable with 1 STA on80 MHz bandwidth, may be defined as another value in consideration ofthe signaling for the number of STUs allocated with 1 STA.

According to an embodiment of the present invention, a virtualallocation resource unit including a tone corresponding to a combinationof at least one BTU and at least one STU may be defined, and a resourceallocation based on the virtual allocation resource unit may beperformed. The resource allocation based on the virtual allocationresource unit may also be called virtualization.

The virtual allocation resource unit may be a resource unit forreutilizing an interleaver size and OFDM numerology of the existing WLANsystem. Further, the virtual allocation resource unit may be defined asa resource unit which is greater than that of BTU and STU andcorresponds to the tone corresponding to the combination of at least oneBTU and at least one STU. For example, the virtual allocation resourceunit may be 242 tones which is the combination of 2 BTUs and 5 STUs and484 tones which is the combination of 4 BTUs and 10 STUs.

Specifically, when 242 tones corresponding to 2 BTUs and 5 STUs areallocated to one STA, the existing pilot allocation and the existinginterleaver size may be utilized. Specifically, the pilot tone may beallocated to 8 tones among 242 tones, and the data tone may be allocatedto the remaining 234 tones. An interleaving based on the interleaver of234 size may be performed for the 234 data tones.

In such a case, a data interleaving procedure and a pilot tone insertionprocedure may be performed in the same manner as that of the existingSTA having been allocated 242 tones. Namely, even when the 242 tonestructure is not physically supported, the resource unit of one virtual242 tones may be allocated to the STA. In such a case, the interleavingprocedure which utilizes the existing interleaver of the 234 size andthe insertion procedure of the existing pilot tones (8 pilot tones) maybe used. Such a 242 tone resource unit may be expressed as the term“virtual allocation resource unit”. The virtual allocation resource unitmay be 242 tones or a multiple number of 242 tones (e.g., 484, 968,etc.). Further, the size of the virtual allocation resource unit may bedetermined based on another interleaver size (108, 52, 24, etc.) havingbeen used in the existing WLAN system. Further, the virtual allocationresource unit may be defined as a resource unit greater than that of BTUand STU corresponding to the tone corresponding to the combination of atleast one BTU and at least one STU and may include a plurality of datatones interleaved by a newly defined interleaver size.

Such a virtual allocation resource unit may be utilized for transmissionbased on SU (single) OFDMA. Further, all BTUs and all STUs defined ineach bandwidth with respect to one STA may be allocated for transmissionbased on SU OFDMA.

The maximum number of STAs which may be simultaneously allocatedresources in 20 MHz bandwidth may be 7. Each of the maximum 7 STAs maybe allocated each of 2 BTUs and 5 STUs. The maximum number of STAs whichmay be allocated resources in 40 MHz bandwidth may be 14. Each of themaximum 14 STAs may be allocated each of 4 BTUs and 10 STUs. The maximumnumber of STAs which may be allocated resources in 80 MHz may be 29.Each of 29 STAs may be allocated each of 8 BTUs and 21 STUs. Further,the maximum number of STAs which may be allocated resources in theentire bandwidth may be limited to a number smaller than 29 (e.g., 20),and in such a case, the maximum 19 STAs may be simultaneously allocatedresources based on the combination of 8 BTUs and 21 STUs in 80 MHz.

According to an embodiment of the present invention, a tone numerologymay be assumed for a size of each bandwidth as follows. The followingtone numerology is provided as one example, and thus a resource may beallocated on the basis of not only the tone numerology disclosed in theexample but also various tone numerologies.

Six left guard tones, three DC tones, and five right guard tones may beassumed for a 20 MHz bandwidth, and an OFDMA tone structure may beconfigured on the basis of two 56-tone resource units (BTUs) and five26-tone resource units (STUs). Alternatively, the resource may beallocated on the basis of a virtual allocation resource unitcorresponding to nine 26-tone resource units. More specifically, theallocation of the two 56-tone resource units (BTUs) and the five 26-toneresource units (STUs) on the 20 MHz bandwidth may be based on: (1) leftguard tone/56/26/26/13/DC/13/26/26/56/right guard tone; or (2)26/26/13/56/DC/56/13/26/26/left guard tone. In this case, 13 tones maybe a resource unit obtained by dividing a 26-tone resource unit.

Six left guard tones, nine DC tones, and five right guard tones may beassumed for a 40 MHz bandwidth. The remaining available 492 tones exceptthe left guard tone, the DC tone, and the right guard tone may bedivided into two parts with respect to the DC tone, and the two partsmay respectively include three 56-tone resource units and three 26-toneresource units. More specifically, the resource allocation on the 40 MHzbandwidth may be based on a left guard tone/56/56/26/26/26/56/DCtone/56/26/26/26/56/56/right guard tone.

Alternatively, six left guards, five DC tones, and five right guardtones may be assumed for the 40 MHz bandwidth. Seven 56-tone resourceunits and four 26-tone resource units may be allocated for available 496tones. More specifically, the resource allocation on the 40 MHzbandwidth may correspond to a left guardtone/56/56/26/26/56/28/DC/28/56/26/26/56/56/right guard tone. In thiscase, 26 tones may be a resource unit obtained by dividing a 56-toneresource unit.

11 left guard tones, 9 DC tones, and 5 right guard tones or 6 left guardtones, 13 DC guard tones, and 5 right guard tones may be assumed for an80 MHz bandwidth. The remaining available 1000 tones except the leftguard tone, the DC tone, and the right guard tone may be divided intofour parts. Four units of 250 tones may be generated by dividing 1000tones. For each of the four units of 250 tones, four 56-tone resourceunits and one 26-tone resource unit may be defined. That is, the 56-toneresource unit and one 26-tone resource unit may be allocated on one unitof 250 tones. Alternatively, the 56-tone resource unit may be dividedinto two 26-tone resource units, and in this case, the 250-tone resourceunit may include nine 26-tone resource units. The nine 26-tone resourceunits may be defined as one virtual allocation resource unit.

More specifically, the resource allocation on the 80 MHz bandwidth maybe based on a left guard tone/56/56/56/56/26/26/56/56/56/56/DCtone/56/56/56/56/26/26/56/56/56/56/right guard tone.

Hereinafter, a method of allocating a pilot tone in a resource unit isdisclosed according to an embodiment of the present invention.

FIG. 3 is a conceptual view illustrating a method of allocating a pilottone for a virtual allocation resource unit according to an embodimentof the present invention.

A method disclosed in FIG. 3 is a method of allocating a pilot tone in avirtual allocation resource unit by considering a position of a pilottone of each of at least one BTU and at least one STU corresponding tothe virtual allocation resource unit. The virtual allocation resourceunit may not use the existing 242-tone based OFDM numerology in theallocation of the pilot tone.

Referring to FIG. 3, the virtual allocation resource unit of 242 tonesmay be allocated through virtualization, and the virtual allocationresource unit of 242 tones may correspond to a combination of 2 BTUs and5 STUs. The BTU may be replaced with 2 STUs. That is, a band plan with astructure of 9 STUs in total may be configured, and this may be used asan allocation resource of 242 tones.

A position of a pilot tone included in a virtual allocation resourceunit (e.g., 242 tones) according to an embodiment of the presentinvention may be the same as a position of all or some pilot tones amonga plurality of pilot tones of at least one BTU (e.g., 2 BTUs) and atleast one STU (e.g., 5 STUs) corresponding to the virtual allocationresource unit. When one BTU is replaced with two STUs, the position ofthe pilot tone included in the virtual allocation resource unit may bethe same as the position of all or some pilot tones among a plurality ofSTUs corresponding to the virtual allocation resource unit.

In other words, a set of positions of pilot tones of the virtualallocation resource unit may be included in a set of positions of aplurality of pilot tones of at least one BTU (e.g., 2 BTUs) and at leastone STU (e.g., 5 STUs) corresponding to the virtual allocation resourceunit.

For example, one BTU may include 4 pilot tones, and one STU may include2 pilot tones. In this case, the total number of pilot tones of the 2BTUs and the 5 STUs may be 18 (=2*4+5*2). Positions of 8 pilot tones outof the 18 pilot tones may be the same as (or overlap with) positions of8 pilot tones included in the virtual allocation resource unit of 242tones.

As shown in FIG. 3, positions of 4 pilot tones out of 8 pilot tonesincluded in the 2 BTUs may be the same as positions of 4 pilot tones ofthe virtual allocation resource unit. The 4 pilot tones included in the2 BTUs having the same position as the position of the pilot tone of thevirtual allocation resource unit may be an even pilot tone (or an evenindex pilot tone). Alternatively, the 4 pilot tones included in the 2BTUs having the same position as the position of the pilot tone of thevirtual allocation resource unit may be an odd pilot tone (or an oddindex pilot tone). Alternatively, the 4 pilot tones included in the 2BTUs having the same position as the position of the pilot tone of thevirtual allocation resource unit may be a combination of the even indexpilot tones/odd index pilot tones.

The even index pilot tone (or even pilot tone) may be a pilot tonelocated at an even position with respect to a leftmost tone or arightmost tone among pilot tones included in a resource unit (BTU, STU),and the odd index pilot tone (or odd pilot tone) may be a pilot tonelocated at an odd position with respect to a specific frequency positionamong the pilot tones included in the resource unit.

In addition, positions of 4 pilot tones out of 8 pilot tones included in4 STUs may be the same as positions of 4 pilot tones of the virtualallocation resource unit. The 4 pilot tones included in 4 STUs havingthe same position as the position of the pilot tone of the virtualallocation resource unit may be even index pilot tones. Alternatively,the 4 pilot tones included in 4 STUs having the same position as theposition of the pilot tone of the virtual allocation resource unit maybe odd index pilot tones. Alternatively, the 4 pilot tones included in 4STUs having the same position as the position of the pilot tone of thevirtual allocation resource unit may be a combination of the even indexpilot tones/odd index pilot tones.

Positions of 2 pilot tones included in the remaining one STU may not bethe same as the position of the pilot tone of the virtual allocationresource unit. The remaining one STU may be a central STU located at thecenter on 242 tones.

That is, as described above, positions of 8 pilot tones out of 18 pilottones of the 2 BTUs and the 5 STUs may be the same as positions of 8pilot tones included in the virtual allocation resource unit of 242tones.

In addition, if one BTU consists of 2 STUs, positions of 8 pilots out of18 pilot tones of 9 STUs may be the same as positions of 8 pilot tonesincluded in the virtual allocation resource unit of 242 tones.

FIG. 4 is a conceptual view illustrating a method of allocating a pilottone for a virtual allocation resource unit according to an embodimentof the present invention.

A method disclosed in FIG. 4 is a method of allocating a pilot tone in avirtual allocation resource unit by considering a position of a pilottone of each of at least one BTU and at least one STU corresponding tothe virtual allocation resource unit. That is, the virtual allocationresource unit may not use the existing 242-tone based OFDM numerology inthe allocation of the pilot tone.

Referring to FIG. 4, the virtual allocation resource unit of 246 tonesmay be allocated through virtualization, and the virtual allocationresource unit of 246 tones may be a combination of 3 BTUs and 3 STUs. Inthe virtual allocation resource unit of 246 tones, only 242 tones may beused as data tones and pilot tones, and 4 tones may be the remainingtones (or leftover tones). Therefore, an interleaving procedure for thedata tone utilizing the existing interleaver of a 234 size may also beused for the virtual allocation resource unit of 246 tones.

According to an embodiment of the present invention, a position of apilot tone included in a virtual allocation resource unit (e.g., 246tones) may be the same as a position of all or some pilot tones among aplurality of pilot tones of at least one BTU (e.g., 3 BTUs) and at leastone STU (e.g., 3 STUs) corresponding to the virtual allocation resourceunit. In other words, a set of positions of pilot tones of the virtualallocation resource unit may be included in a set of positions of aplurality of pilot tones of at least one BTU (e.g., 3 BTUs) and at leastone STU (e.g., 3 STUs) corresponding to the virtual allocation resourceunit.

For example, one BTU may include 4 pilot tones, and one STU may include2 pilot tones. In this case, the total number of pilot tones of the 3BTUs and the 3 STUs may be 18 (=3*4+3*2). Positions of 8 pilot tones outof the 18 pilot tones may be the same as (or overlap with) positions of8 pilot tones included in the virtual allocation resource unit of 246tones.

As shown in FIG. 4, positions of 6 pilot tones out of 12 pilot tonesincluded in the 3 BTUs may be the same as positions of 6 pilot tones ofthe virtual allocation resource unit. 6 pilot tones included in the 3BTUs having the same position as the position of the pilot tone of thevirtual allocation resource unit may be even index pilot tones.Alternatively, the 6 pilot tones included in the 3 BTUs having the sameposition as the position of the pilot tone of the virtual allocationresource unit may be odd index pilot tones. Alternatively, the 6 pilottones included in the 3 BTUs having the same position as the position ofthe pilot tone of the virtual allocation resource unit may be acombination of the even index pilot tones/odd index pilot tones.

In addition, positions of 2 pilot tones out of 4 pilot tones included in2 STUs may be the same as positions of 2 pilot tones of the virtualallocation resource unit. 2 pilot tones included in 2 STUs having thesame position as the position of the pilot tone of the virtualallocation resource unit may be even index pilot tones. Alternatively,the 2 pilot tones included in 2 STUs having the same position as theposition of the pilot tone of the virtual allocation resource unit maybe odd index pilot tones. Alternatively, the 2 pilot tones included in 2STUs having the same position as the position of the pilot tone of thevirtual allocation resource unit may be a combination of the even indexpilot tones/odd index pilot tones.

Positions of 2 pilot tones included in the remaining one STU may notoverlap with the position of the pilot tone of the virtual allocationresource unit. The remaining one STU may be a central STU located at thecenter on 246 tones.

That is, as described above, positions of 6 pilot tones out of 18 pilottones of the 3 BTUs and the 3 STUs may be set to be the same aspositions of 8 pilot tones included in the virtual allocation resourceunit of 246 tones.

If a position of a pilot tone is allocated as disclosed in FIG. 3 andFIG. 4, the position of the pilot may be fixed instead of varyingdepending on a change in a resource unit to be allocated, therebyproviding convenience in implementation. For example, if a pilot tone ofa virtual allocation resource unit corresponds to some pilot tones amongpilot tones included in a BTU and STU that can be allocated in abandwidth (in other words, if a position of the pilot tone of thevirtual allocation resource unit corresponds to a position of some pilottones among pilot tones included in the BTU and STU that can beallocated in the bandwidth or if a set of positions of pilot tones ofthe virtual allocation resource unit is included in a set of positionsof some pilot tones among the pilot tones included in the BTU and STUthat can be allocated in the bandwidth), a long training field(LTF)-based operation and a channel tracking operation may be easilyimplemented.

According to another embodiment of the present invention, a position ofat least one pilot tone among a plurality of pilot tones included in theBTU and STU that can be allocated in the bandwidth may be set to be thesame as the position of the pilot tone of the virtual allocationresource unit by considering an interpolation/extrapolationcharacteristic.

Alternatively, a position of at least one pilot tone among a pluralityof pilot tones included in the BTU and STU that can be allocated in thebandwidth may be set to be the same as the position of the pilot tone ofthe virtual allocation resource unit by considering a structure of atraining field supported in a WLAN system (an HE-LTF structure generatedbased on 4× IFFT).

Likewise, if the position of the pilot tone is allocated, the positionof the pilot may be fixed instead of varying depending on a change in aresource unit to be allocated, thereby providing convenience inimplementation. For example, if a pilot tone of a virtual allocationresource unit corresponds to some pilot tones among pilot tones includedin a BTU and STU that can be allocated in a bandwidth (in other words,if a position of the pilot tone of the virtual allocation resource unitcorresponds to a position of some pilot tones among pilot tones includedin the BTU and STU that can be allocated in the bandwidth), a longtraining field (LTF)-based operation and a channel tracking operationmay be easily implemented.

According to another embodiment of the present invention, a position ofat least one pilot tone among a plurality of pilot tones included in theBTU and STU that can be allocated in the bandwidth may overlap with theposition of the pilot tone of the virtual allocation resource unit byconsidering an interpolation/extrapolation characteristic.

Alternatively, a position of at least one pilot tone among a pluralityof pilot tones included in the BTU and STU that can be allocated in thebandwidth may overlap with the position of the pilot tone of the virtualallocation resource unit by considering a structure of a training fieldsupported in a WLAN system (an HE-LTF structure generated based on 4×IFFT).

FIG. 5 is a conceptual view illustrating a method of allocating a pilottone in a PPDU according to an embodiment of the present invention.

The pilot tone allocation method disclosed in FIG. 3 and FIG. 4 isapplied to the PPDU of FIG. 5.

Among fields included in the PPDU, a field by which an STA must performdecoding without knowing whether a resource allocated to the STA is avirtual allocation resource or a BTU and/or an STU may be expressed by aresource unspecified field 500. On the contrary, among the fieldsincluded in the PPDU, a field by which the STA can perform decoding byknowing whether the resource allocated to the STA is the virtualallocation resource or the BTU and/or the STU may be expressed by aresource specified field 540.

The virtual allocation resource unit for transmitting the resourceunspecified field 500 may include a pilot tone corresponding topositions of all pilot tones of at least one BTU and at least one STUcorresponding to the virtual allocation resource unit. As a specificexample, the virtual allocation resource unit of 246 tones fortransmitting the resource unspecified field 500 may include 18 pilottones corresponding to positions of 18 pilot tones included in 2 BTUsand 5 STUs. In other words, a set of pilot tones of the virtualallocation resource unit of 246 tones may be the same as a set of 18pilot tones included in the 2 BTUs and the 5 STUs corresponding to thevirtual allocation resource unit of 246 tones.

For example, the resource unspecified field 500 may be a training fieldtransmitted before a signal field (e.g., a high efficiency (HE)-signal(SIG)) 520 including information on resource allocation (or scheduling)(for example, HE-LTF if the HE-LTF is transmitted before the signalingfield 520). The virtual allocation resource unit for transmitting thetraining field may include 18 pilot tones.

The virtual allocation resource unit for transmitting the resourcespecified field 540 may include a pilot tone corresponding to some pilottones among all pilot tones of at least one BTU and at least one STUcorresponding to the virtual allocation resource unit. As describedabove in FIG. 2 and FIG. 3, the virtual allocation resource unit of 246tones for transmitting the resource specified field 540 may include 8pilot tones corresponding to positions of 8 pilot tones among 18 pilottones included in 2 BTUs and 5 STUs.

For example, the resource specified field 540 may be a data fieldtransmitted after the signal field 520 including the information on theresource allocation (or scheduling). The virtual allocation resourceunit for transmitting the data field may include 8 pilot tones.

FIG. 6 is a conceptual view illustrating a method of allocating a pilottone according to an embodiment of the present invention.

In FIG. 6, pilot allocation is disclosed in a resource unit having twodifferent sizes for supporting a single OFDMA resource allocationstructure. More specifically, a method of allocating a pilot tone and adata tone is disclosed for a 56-tone resource unit (BTU) 650 and a26-tone resource unit (or STU) 600, respectively.

A pilot tone for the 56-tone resource unit 650 may be determined byconsidering an allocation position and the number of pilot tones/datatones based on a 56-tone numerology used in the existing IEEE 802.11ac.

The allocation position and the number of pilot tones/data tones basedon the 56-tone numerology used in the existing IEEE 802.11ac aredisclosed in 22.3.10.10 Pilot subcarriers of IEEE Standard forInformation technology telecommunications and information exchangebetween systems local and metropolitan area networks specificrequirements ‘Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) Specifications Amendment 4: Enhancements for VeryHigh Throughput for Operation in Bands below 6 GHz.

The 26-tone resource unit 600 may be determined by considering anallocation position and the number of pilot tones/data tones based on a26-tone numerology used in the existing IEEE 802.11ah.

The allocation position and the number of pilot tones/data tones basedon the 26-tone numerology used in the existing IEEE 802.11ah aredisclosed in 24.3.9.10 Pilot subcarriers of IEEE P802.11ah™/D5.0 DraftStandard for Information technology telecommunications and informationexchange between systems Local and metropolitan area network specificrequirements ‘Part 11: Wireless LAN Medium Access Control (MAC) andPhysical Layer (PHY) SpecificationsAmendment 2: Sub 1 GHz LicenseExemptOperation’.

Referring to FIG. 6, a pilot tone may be located at [x y] in the 26-toneresource unit 600. [x y] may be determined such that an interval betweenpilot tones has 14 tones. That is, [x y] may be set such that a pilottone spacing corresponds to 14 tones. For example, a tone located at a7^(th) position in a direction of increasing a frequency with respect toa specific tone may be defined as a 1^(st) pilot tone, and a tonelocated at a 7^(th) position in a direction of decreasing the frequencymay be defined as a 2^(nd) pilot tone. In this case, [x y] may be [−7+7]with respect to the specific tone.

The pilot tone may be located at [a x y b] in the 56-tone resource unit650. [a x y b] may be determined such that an interval between pilottones has 14 tones. More specifically, a pilot tone interval of a and x,a plot tone interval of x and y, and a pilot tone interval of y and bmay corresponding to 14 tones. For example, tones located at 7^(th) and21^(st) positions in a direction of increasing a frequency with respectto a specific tone may be defined respectively as 1^(st) and 2^(d)second pilot tones, and tones located at 7^(th) and 21^(st) positions ina direction of decreasing the frequency may be defined respectively as3^(rd) and 4^(th) pilot tones. In this case, [a x y b] may be[−21−7+7+21] with respect to the specific tone.

FIG. 7 is a conceptual view illustrating a method of allocating a pilottone according to an embodiment of the present invention.

In FIG. 7, pilot allocation is disclosed in a resource unit having twodifferent sizes for supporting a single OFDMA resource allocationstructure. In particular, allocation of a pilot tone is disclosed when a56-tone resource unit is allocated by being divided into two 26-toneresource units and four leftover tones. In addition, allocation of apilot tone is disclosed when the two 26-tone resource units and anadditional leftover tone are combined to be allocated as a 56-toneresource unit.

Positions of two 26-tone resource units generated by dividing the56-tone resource unit may be allocated by considering a position of apilot tone in the 56-tone resource unit. In addition, if the two 26-toneresource units and the additional leftover tone are combined to beallocated as the 56-tone resource unit, a position of a pilot tone forthe 56-tone resource unit may be allocated by considering a position ofa pilot tone in the 26-tone resource unit constituting the 56-toneresource unit.

Referring to FIG. 7, one 56-tone resource unit 700 fixed on a frequencyaxis may be divided into two 26-tone resource units 710 and 720 fixed onthe frequency axis. In other words, the 56-tone unit 700 fixed on thefrequency axis may be virtually allocated to the two 26-tone units 710and 720 fixed on the frequency axis. Such a resource unit division maybe performed when there is a need to allocate resources for a pluralityof STAs.

If a position of a pilot tone of the 56-tone resource unit 700 is [a x yb], a position of a pilot tone of the 1^(st) 26-tone resource unit 710generated by dividing the 56-tone resource unit may be [a x], and aposition of a pilot tone of the 2^(nd) 26-tone resource unit 720 may be[y b]. In this case, as described above, [a, x, y, b] may be [−21, −7,+7, +21] with respect to the specific tone. That is, even if the 56-toneresource unit 700 is divided and used, a pilot spacing and/or a pilotposition may be maintained in the 56-tone resource unit 700. Inaddition, from a perspective of the 26-tone resource units 710 and 720,a pilot spacing and/or a pilot position of the 26-tone resource units710 and 720 may also be maintained on the basis of the pilot tonesallocated to [a x] and [y b].

That is, in the pilot tone allocation method according to the embodimentof the present invention, even if the 56-tone resource unit 700 isdivided, not only the pilot spacing and pilot position of one 56-toneresource unit 700 but also the pilot spacing and/or pilot position ofthe 26-tone resource units 710 and 720 may be maintained.

On the contrary, if the two 26-tone resource units 710 and 720 and anadditional leftover tone are combined and allocated as the 56-toneresource unit 700, a pilot spacing and/or pilot position of the two26-tone resource units 710 and 720 may be maintained.

For example, if a position of a pilot tone of the 1^(st) 26-toneresource unit 710 is [a x] and a position of a pilot tone of the 2^(nd)26-tone resource unit 720 is [y b], a position of a pilot tone of the56-tone resource unit 700 may be [a x y b]. From a perspective of theindividual 26-tone resource units 710 and 720, [a x]=[−7+7] and [by]=[−7+7] may be satisfied. In addition, from a perspective of the56-tone resource unit 700, [a x y b] may be [−21, −7, +7, +21].

That is, even if the 26-tone resource units 710 and 720 are combined toconstitute the 56-tone resource unit 700, not only a pilot spacing andpilot position of the 26-tone resource units 710 and 720 but also apilot spacing and/or pilot position of the 56-tone resource unit 700 maybe maintained.

FIG. 8 is a flowchart illustrating a scheduling method of a wirelessresource according to an embodiment of the present invention.

In FIG. 8, a method of scheduling a wireless resource by an AP on thebasis of a BTU and/or an STU is disclosed.

The AP schedules each of a plurality of wireless resources forcommunication with a plurality of STAs on a bandwidth (step S800).

For example, each of the plurality of wireless resources may be one of afirst resource unit, a second resource unit, a combination of the firstresource unit and the second resource unit, and a virtual allocationresource unit.

The virtual allocation resource unit may be a combination of at leastone first resource unit and at least one second resource unit includinga plurality of data tones that can be interleaved by one interleaver.

If at least one wireless resource among the plurality of wirelessresources is the virtual allocation resource unit, a set of positions ofa plurality of first pilot tones included in the virtual allocationresource unit may be included in a set of positions of a plurality ofsecond pilot tones included in at least one first resource unit and atleast one second resource unit constituting the virtual allocationresource unit.

As described above, each of the at least one first resource unitconstituting the virtual allocation resource unit may be a BTUcorresponding to 56 tones including 52 data tones and 4 second pilottones. The 4 second pilot tones may include 2 even index pilot toneslocated at an even position with respect to a specific tone and 2 oddindex pilot tones located at an odd position with respect to thespecific tone.

In addition, each of the at least one second resource unit constitutingthe virtual allocation resource unit may be an STU corresponding to 26tones including 24 data tones and 2 second pilot tones. The 2 secondpilot tones may include 1 even index pilot tone located at an evenposition with respect to a specific tone and 1 odd index pilot tonelocated at an odd position with respect to the specific tone.

In the above case, the positions of the plurality of first pilot tonesincluded in the virtual allocation resource unit may be the same aspositions of 2 even index pilot tones of each of at least one firstresource unit constituting the virtual allocation resource unit and theposition of 1 even index pilot tone of each of the remaining secondresource units except 1 second resource unit among at least 1 secondresource unit constituting the virtual allocation resource unit.

Alternatively, the positions of the plurality of first pilot tonesincluded in the virtual allocation resource unit may be the same aspositions of 2 odd index pilot tones of each of at least one firstresource unit constituting the virtual allocation resource unit and theposition of 1 odd index pilot tone of each of the remaining secondresource units except 1 second resource unit among at least one secondresource unit constituting the virtual allocation resource unit.

In addition, according to an embodiment of the present invention, if aresource unspecified field is transmitted through the virtual allocationresource unit, positions of a plurality of first pilot tones included inthe virtual allocation resource unit may be the same as positions of aplurality of second pilot tones included in at least one first resourceunit and at least one second resource unit constituting the virtualallocation resource unit.

In addition, according to an embodiment of the present invention, if aresource specified field is transmitted through the virtual allocationresource unit, positions of a plurality of first pilot tones included inthe virtual allocation resource unit may be the same as positions ofsome second pilot tones among a plurality of second pilot tones includedin at least one first resource unit and at least one second resourceunit constituting the virtual allocation resource unit.

The resource unspecified field may be a field transmitted before asignal field including allocation information for the virtual allocationresource unit, and the resource specified field may be a fieldtransmitted after the signal field.

The AP transmits a plurality of pieces of downlink data respectively tothe plurality of STAs respectively through a plurality of wirelessresources (step S810).

The plurality of pieces of downlink data (or downlink PPDU) may betransmitted respectively to the plurality of STAs respectively throughthe plurality of wireless resources scheduled in step S800.

FIG. 9 is a conceptual view illustrating a DL MU PPDU format accordingto an embodiment of the present invention.

In FIG. 9, a DL MU PPDU format transmitted based on OFDMA by an AP isdisclosed according to the embodiment of the present invention.

Referring to an upper portion of FIG. 9, a PHY header of a DL MU PPDUmay include a legacy-short training field (L-STF), a legacy-longtraining field (L-LTF), a legacy-signal (L-SIG), a highefficiency-signal A (HE-SIG A), a high efficiency-signal-B (HE-SIG B), ahigh efficiency-short training field (HE-STF), a high efficiency-longtraining field (HE-LTF), and a data field (or a MAC payload). The PHYheader may be divided into a legacy part before the L-SIG and a highefficiency (HE) part after the L-SIG.

An L-STF 900 may include a short training orthogonal frequency divisionmultiplexing (OFDM) symbol. The L-STF 900 may be used for framedetection, automatic gain control (AGC), diversity detection, and coarsefrequency/time synchronization.

An L-LTF 910 may include a long training OFDM symbol. The L-LTE 910 maybe used for fine frequency/time synchronization and channel prediction.

An L-SIG 920 may be used to transmit control information. The L-SIG 920may include information for a data rate and a data length.

An HE-SIG A 930 may include information for indicating an STA forreceiving a DL MU PPDU. For example, the HE-SIG A 930 may include anidentifier of a specific STA (or AP) for receiving the PPDU andinformation for indicating a group of the specific STA. Further, if theDL MU PPDU is transmitted based on orthogonal frequency divisionmultiple access (OFDMA) or multiple input multiple output (MIMO), theHE-SIG A 930 may also include resource allocation information forreceiving the DL MU PPDU of the STA.

Further, the HE-SIG A 930 may include color bits information for BSSidentification, bandwidth information, a tail bit, a CRC bit, modulationand coding scheme (MCS) information for an HE-SIG B 940, symbol countinformation for the HE-SIG B 940, and cyclic prefix (CP) (or guardinterval (GI)) length information.

The HE-SIG B 940 may include a length of physical layer service dataunit (PSDU) for each STA, information regarding modulation and codingscheme (MCS), a tail bit, or the like. Further, the HE-SIG B 940 mayinclude information for the STA for receiving the PPDU and OFDMA-basedresource allocation information (or MU-MIMO information). If theOFDMA-based resource allocation (or MU-MIMO related information) isincluded in the HE-SIG B 940, resource allocation information may not beincluded in the HE-SIG A 930.

An HE-SIG A 950 or an HE-SIG B 960 may include resource allocationinformation (or virtual resource allocation information) for each of theplurality of STAs or resource allocation information such as informationregarding whether resource allocation is performed by using only a BTUor an STU.

A field prior to the HE-SIG B 940 on the DL MU PPDU may be transmittedin a duplicated form in each of different transmission resources. Incase of the HE-SIG B 940, the HE-SIG B 940 transmitted in somesubchannels (e.g., subchannel 1, subchannel 2) may be an independentfield containing individual information, and the HE-SIG B 940transmitted in the remaining subchannels (e.g., subchannel 3, subchannel4) may have a format in which the HE-SIG B 940 transmitted in othersubchannels (e.g., subchannel 1, subchannel 2)) is duplicated.Alternatively, the HE-SIG B 940 may be transmitted on all transmissionresources in an encoded form. A field next to the HE-SIG B 940 mayinclude individual information for each of the plurality of STAs forreceiving the PPDU.

The HE-STF 950 may be used to improve automatic gain control estimationin an MIMO environment or an OFDMA environment.

More specifically, an STA1 may receive an HE-STF1 transmitted through aresource unit1 from the AP, and may decode a data field1 by performingsynchronization, channel tracking/prediction, and AGC. Similarly, anSTA2 may receive an HE-STF2 transmitted through a resource unit2 fromthe AP, and may decode a data field2 by performing synchronization,channel tracking/prediction, and AGC. An STA3 may receive an HE-STF3transmitted through a resource unit3 from the AP, and may decode a datafield3 by performing synchronization, channel tracking/prediction, andAGC. An STA4 may receive an HE-STF4 transmitted through a resource unit4from the AP, and may decode a data field4 by performing synchronization,channel tracking/prediction, and AGC.

The HE-LTF 960 may be used to estimate a channel in the MIMO environmentor the OFDMA environment.

A size of IFFT applied to the HE-STF 950 and a field next to the HE-STF950 may be different from a size of IFFT applied to a field prior to theHE-STF 950. For example, the size of IFFT applied to the HE-STF 950 andthe field next to the HE-STF 950 may be four times greater than the sizeof IFFT applied to the field prior to the HE-STF 950. The STA mayreceive the HE-SIG A 930, and may be instructed to receive a downlinkPPDU on the basis of the HE-SIG A 930. In this case, the STA may performdecoding on the HE-STF 950 and the field next to the HE-STF 950 on thebasis of a changed FFT size. On the contrary, if the STA is notinstructed to receive the downlink PPDU on the basis of the HE-SIG A930, the STA may stop decoding and may configure a network allocationvector (NAV). A cyclic prefix (CP) of the HE-STF 950 may have a sizegreater than a CP of another field, and for this CP duration, the STAmay perform decoding on the downlink PPDU by changing the FFT size.

An access point (AP) may allocate a plurality of wireless resources fora plurality of stations (STAs) respectively on a full bandwidth, and maytransmit a physical protocol data unit (PPDU) to each of the pluralityof STAs through each of the plurality of wireless resources. Allocationinformation of the plurality of wireless resources respectively for theplurality of STAs may be included in the HE-SIG A 930 or the HE-SIG B930 as described above.

In this case, each of the plurality of wireless resources may be acombination of a plurality of wireless resource units (BTU, STU) havingdifferent sizes by definition on a frequency axis. As described above,the resource allocation combination may be a combination of at least oneresource unit that can be allocated on all available tones depending ona bandwidth size.

FIG. 10 is a conceptual view illustrating transmission of a UL MU PPDUaccording to an embodiment of the present invention.

Referring to FIG. 10, a plurality of STAs may transmit the UL MU PPDU onthe basis of UL MU OFDMA to an AP.

An L-STF 1000, an L-LTF 1010, an L-SIG 1020, an HE-SIG A 1030, and anHE-SIG B 1040 may perform the function disclosed in FIG. 9. Informationincluded in a signal field (the L-SIG 1020, the HE-SIG A 1030, and theHE-SIG B 1040) may be generated based on information included in asignal field of a received DL MU PPDU.

The STA1 may perform uplink transmission through a full bandwidth untilthe HE-SIG B 1040, and may perform uplink transmission through anallocated bandwidth starting from an HE-STF 1050. The STA1 may deliveran uplink frame on the basis of a UL MU PPDU through an allocatedbandwidth (e.g., a resource unit1). An AP may allocate an uplinkresource of each of a plurality of STAs on the basis of the DL MU PPDU(e.g., HE-SIG A/B). Upon allocating the uplink resource, each of theplurality of STAs may transmit the UL MU PPDU.

FIG. 11 is a block diagram illustrating a wireless device according toan embodiment of the present invention.

Referring to FIG. 11, a wireless device 1100 is an STA capable ofimplementing the aforementioned embodiment, and may be an AP 1100 or anon-AP STA (or STA) 1150.

The AP 1100 includes a processor 1110, a memory 1120, and a radiofrequency (RF) unit 1130.

The RF unit 1130 may be coupled to the processor 1110 totransmit/receive a radio signal.

The processor 1110 may implement the functions, procedures, and/ormethods proposed in the present invention. For example, the processor1110 may be configured to perform an operation of the AP according tothe aforementioned embodiment of the present invention. The processormay perform the operation of the AP disclosed in the embodiment of FIG.1 to FIG. 10.

For example, the processor 1110 may be implemented to schedule each of aplurality of wireless resources for communicating with a plurality ofstations (STAs) on a bandwidth, and to transmit a plurality of pieces ofdownlink data to each of the plurality of STAs through each of theplurality of wireless resources.

At least one wireless resource among the plurality of wireless resourcesmay be a virtual allocation resource unit. The virtual allocationresource unit may be a combination of at least one first resource unit(e.g., BTU) and at least one second resource unit (e.g., STU) includinga plurality of data tones that can be interleaved by one interleaver.

A set of positions of a plurality of first pilot tones included in thevirtual allocation resource unit may be included in a set of positionsof a plurality of second pilot tones included in at least one firstresource unit and at least one second resource unit constituting thevirtual allocation resource unit.

An STA 1150 includes a processor 1160, a memory 1170, and a radiofrequency (RF) unit 1180.

The RF unit 1180 may be coupled to the processor 1160 totransmit/receive a radio signal.

The processor 1160 may implement the functions, procedures, and/ormethods proposed in the present invention. For example, the processor1160 may be configured to perform an operation of the STA according tothe aforementioned embodiment of the present invention. The processor1160 may perform the operation of the STA disclosed in the embodiment ofFIG. 1 to FIG. 10.

For example, if a resource unspecified field transmitted before a signalfield including resource scheduling (or resource allocation) informationis transmitted on a virtual allocation resource unit, the processor 1160may be implemented to perform decoding on a resource unspecified fieldon the basis of a plurality of first pilot tones. In this case,positions of the plurality of first pilot tones may be the same aspositions of all pilot tones of a combination of at least one firstresource unit and at least one second resource unit constituting thevirtual allocation resource unit.

In addition, if a resource specified field transmitted after a signalfield including resource scheduling (or resource allocation) informationis transmitted on the virtual allocation resource unit, the processor1160 may be implemented to perform decoding on the resource specifiedfield on the basis of a plurality of second pilot tones. In this case,the positions of the plurality of second pilot tones may be the same aspositions of some pilot tones among all pilot tones of a combination ofat least one first resource unit and at least one second resource unitconstituting the virtual allocation resource unit.

The processors 1110 and 1160 may include application-specific integratedcircuits (ASICs), other chipsets, logical circuits, data processingdevices, and/or converters for mutually converting a baseband signal anda radio signal. The memories 1120 and 1170 may include a read-onlymemory (ROM), a random access memory (RAM), a flash memory, a memorycard, a storage medium and/or other storage devices. The RF units 1130and 1180 may include at least one antenna to transmit and/or receive theradio signal.

When the above-described embodiment is implemented in software, theabove-described scheme may be implemented using a module (process orfunction) which performs the above function. The module may be stored inthe memories 1120 and 1170 may be and executed by the processors 1110and 1160. The memories 1120 and 1170 may be disposed to the processors1110 and 1160 internally or externally and connected to the processors1110 and 1160 using a variety of well-known means.

What is claimed is:
 1. A method for supporting operations of a wirelessdevice in a wireless local area network (WLAN), the method comprising:generating, by an access point (AP), a physical layer protocol data unit(PPDU) including a plurality of resource units on a bandwidth, whereinthe plurality of resource units include a first tone unit related to asecond tone unit, wherein the first tone unit includes a total of 26tones, wherein 2 pilot tones are included in the total of 26 tones forthe first tone unit, wherein the second tone unit includes a pluralityof tones being greater than the first tone unit, and wherein 4 pilottones are included in the plurality of tones for the second tone unit,and wherein the 2 pilot tones are aligned on a frequency location with aportion of the 4 pilot tones; and transmitting, by the AP, the PPDUbased on the plurality of resource units.
 2. The method of claim 1,wherein allocation information for the plurality of resource units isincluded in a header of the PPDU.
 3. An access point (AP) for supportingoperations of a wireless device in a wireless local area network (WLAN),the AP comprising: a radio frequency (RF) unit for transmitting andreceiving a radio signal; and a processor operatively coupled to the RFunit, wherein the processor is configured for: generating a physicallayer protocol data unit (PPDU) including a plurality of resource unitson a bandwidth, wherein the plurality of resource units include a firsttone unit related to a second tone unit, wherein the first tone unitincludes a total of 26 tones, wherein 2 pilot tones for the STU areincluded in the total of 26 tones for the first tone unit, wherein thesecond tone unit includes a plurality of tones being greater than thefirst tone unit, and wherein 4 pilot tones are included in the pluralityof tones for the second tone unit, and wherein the 2 pilot tones arealigned on a frequency location with a portion of the 4 pilot tones; andtransmitting the PPDU based on the plurality of resource units.
 4. Themethod of claim 3, wherein allocation information for the plurality ofresource units is included in a header of the PPDU.